It has recently been found that many periodic complex cells in area 19 may be of the "periodic" type, i.e. their average response histogram generated by a narrow slit of light at the preferred orientation across the receptive field at the preferred direction consists of a series of four to seven periodically spaced zones of increased excitability. We now wish to study such cells with moving sine-wave gratings so as to determine their spatial frequency selectivity and to find out whether the periodicity found in response to a narrow moving slit predicts the peak of the spatial frequency selectivity found with sine-wave gratings. Such information has recently been obtained for periodic complex cells in the primary visual cortex, and we now wish to determine whether responses of periodic complex cells in area 19 represent a later stage of information processing in terms of spatial frequency selectivity characteristics. BIBLIOGRAPHIC REFERENCE: Bodis-Wollner, I.G., Pollen, D.A. and Ronner, S.F.: Responses of complex cells in the visual cortex of the cat as a function of the length of moving slits. Brain Research 116: 1976, in Press.